The demand for matrix-type displays as simple display devices has recently increased with the increase in the kinds of apparatus containing microcomputers. In addition, since the definition in computer terminal displays and in high-quality televisions is being made increasingly high, it is necessary that display devices using liquid crystals each have an electrode pattern of a high density and that the thickness of a liquid crystal layer sealed between glass substrates be small.
Conventionally, control has been made to the gap in a liquid crystal panel by dispersing spacers having a given diameter on one of the substrates, bonding the upper and lower substrates by a given method, and then setting a sealing resin at a given temperature or by applying UV light while applying a load such as an iron block.
In addition, in order to form more uniform gaps, the method shown in FIG. 6 has been proposed in which substrates 2, 3, which have been subjected to alignment, are inserted into a bag 1 made of a heat-shrinkable film, with uniform pressure being applied to the bag by vacuum packing or heating instead of using the iron block. The method shown in FIG. 7 has also been proposed in which substrates 2, 3, which have been subjected to alignment, are placed in a pressure vessel 4, a partition member 5 made of silicone rubber is fixed thereto, then a pressure fluid such as water or oil is pumped into the vessel by a pump 6, and UV setting is performed by thermal setting or UV irradiation using a mercury lamp 7 in the state wherein the substrates 2, 3 are pressed.
The above-described methods have several problems and thus do not always yield a uniform panel gap and alignment information, resulting in a decrease in the yields of the methods. The method using the bag made of heat-shrinkable film has the following problems:
(1) When the substrates are inserted into the bag made of a heat-shrinkable film, slippage occurs in the alignment of the substrates.
(2) When vacuum packing is performed after the substrates have been inserted into the bag made of a heat-shrinkable film, slippage occurs in the alignment of the substrates. In addition, a jig is required for reducing the slippage, and the number of repetitions is thus increased.
(3) The electrodes on the substrates may be damaged by the additives in the heat-shrinkable film during heating.
(4) The processes of insertion of the substrates into the bag and the extraction therefrom after setting require long working times and cannot be easily provided in a line system.
(5) One bag is required for one pair of substrates, leading to a high cost.
(6) Since beads used as gap materials in some cases spring out from an injection port 8 for a liquid crystal which is interposed between the substrates if the pressure is rapidly reduced during vacuum packing, as shown in FIG. 8, irregularities are produced in the gap. These irregularities in the gap can be observed as the interference fringes shown in the drawing by irradiation of Na rays.
The method using a pressure fluid for pressing has the following problems:
(7) When the partition member made of silicone rubber is fixed, slippage occurs in the alignment of the two substrates.
(8) When the pressure fluid flows into the vessel after the partition member has been fixed, slippage also occurs in the alignment of the two substrates.
(9) Since it is necessary to sufficiently consider a sealed structure of the apparatus which is thus made large, the cost is thus increased.
(10) Since the pressure fluid is caused to flow and to be discharged for each of two substrates, the working time is increased.
(11) If a filter containing an organic dye, etc. is formed on the substrates when UV light is applied, a change in the properties of the organic dye or decomposition thereof takes place in some cases.